This is a small experiment to create a waterfall plot with HTML Canvas and WebSockets to stream live FFT data from an SDR:
spectrum.js contains the main JavaScript source code for the plot, while colormap.js contains colormaps generated using make_colormap.py.
index.html, style.css, script.js contain an example page that receives FFT data on a WebSocket and plots it on the waterfall plot.
server.py contains a example Bottle and gevent-websocket server that broadcasts FFT data to connected clients. The FFT data is generated using GNU radio using a USRP but it should be fairly easy to change it to a different SDR.